The present invention relates to microfluidic devices having integral porous regions.
This invention relates to the microfluidic devices that contain built-in means for controlling fluid flow. In one aspect of the present invention, certain sections of microfluidic channels contain porous materials that inhibit fluid flow. These sections are referred to herein as porous regions. In use, when fluid encounters these regions, fluid flow will be inhibited until sufficient pressure is provided for the fluid to overcome the impedance provided by the porous materials.
In certain embodiments, these microfluidic device comprise sandwiched stencils as in U.S. patent application Ser. No. 09/453,029, filed Dec. 2, 1999, now abandoned; and as in the substantially identical WIPO published application number WO 01/25138, filed Oct. 4, 2000, published Apr. 12, 2001, and now abandoned. The impedance regions can be constructed within the channels in a number of ways. In a preferred embodiment, porous materials are inserted into or between channels to form the impedance region. In another preferred embodiment, the impedance region is a sheet or layer of material that forms one of the stencil layers of the device. Fluid travels through channels in one layer of a device and passes through vias (apertures between layers) that lead through the stencil layer composing the impedance region to channels on an upper or lower layer of the device. In other embodiments, an impedance region may be constructed by inserting or flowing one or more ingredients into a channel and allowing the ingredients to partially or fully solidify, such as by partial or complete evaporation. The flowing ingredient(s) from which the impedance region is constructed may be a liquid, slurry, or suspension of polymers, inorganic materials, or other materials known in the filtering art.
Multiple porous regions described here can be built into a single microfluidic device. The porous regions can have similar or very different impedances, depending on numerous factors including the composition of the materials or geometry used to construct the porous regions.